General Knowledge- Physics ( Work, Energy and Power)

Work, Energy and Power

Work: If a body gets displacement when a force acts on it, work is said to be done. Work is defined as the product of force and displacement of the body along the direction of the force.

If a body gets displaced by S when force F acts on it.

Then the work W =FS cos θ

Where θ = angle between displacement and force.

If both force and the displacement is in the same direction, then W =FS

Work is scalar quantity and its SI unit is Joule.

Energy: Capacity of doing work by a body is called energy.

► Energy is a scalar quantity and its SI unit is joule.

► Energy developed in a body due to work done on it is called mechanical energy. Mechanical Energy is of two types:

(i)                 Potential Energy

(ii)               Kinetic Energy

Potential Energy: The capacity of doing work developed in a body due to its position or configuration is called its potential energy.

            Example:

(i)                 Energy of stretched or compressed spring

(ii)               Energy of water collected at a height

(iii)             Energy of spring in a watch.

Potential energy of a body in the gravitational field of the earth is mgh.

Where m = mass, g = acceleration due to gravity and h = height of the body from the surface of the earth.

Kinetic Energy: Energy posses by a body due to its motion are called Kinetic Energy of the body.

If a body of mass m is moving with a speed of v, the kinetic energy of the body is ½ mv²

i.e. Kinetic Energy = ½ mv²

Principal of Conservation of Energy:  Energy can neither be created nor can be destroyed. Only energy can be transformed from one form to another form. Whenever energy is utilized in one form, equal amount of energy is produced in other form. Hence total energy of the universe remains the same. This is called the principal of conservation of energy.

Some Equipment used to transform Energy

S.No.	Equipment	Energy Transformed
1.	Dynamo	Mechanical energy into electrical energy
2.	Candle	Chemical Energy into light and heat energy
3.	Microphone	Sound energy into electrical energy
4.	Loud Speaker	Electrical energy into sound energy
5.	Solar Cell	Solar energy in to electrical energy
6.	Tube light	Electrical energy in to light energy
7.	Electric Bulb	Electrical energy in to light energy
8.	Battery	Chemical energy into electrical energy
9.	Electric Motor	Electrical energy in to mechanical energy
10.	Sitar	Mechanical energy in sound energy

Relation between Momentum and Kinetic Energy

                        K.E = P²/2m where p= momentum = mv

Clearly when momentum is doubled Kinetic energy becomes four times.

Power: Rate of doing work is called power.

 If an agent does w work in t time, then power of agent =W/t

SI unit of power is watt named as a respect to the scientist James Watt.

                        Watt= joule/sec.

                        1 KW = 10³ watt

                        1MW = 10⁶ watt

Horse power is a practical unit of power. 1H.P. = 746 watt.

                        1 watt second = 1 watt* 1 Second = 1joule.

                        1 watt hour (Wh) =3600 joule

                        1 kilowatt hour (kwh) = 3.6*10⁶ joule.

W, kw, MW & H.P. are units of power.

Ws. Wh, kwh are units of work and energy.

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